A common hydrocarbon production system includes a production facility with seafloor wells, and a pipeline connecting the production facility to a storage barge that can store a large quantity of liquid hydrocarbons, or oil, such as 40 days of production. At intervals such as every month, an offloading tanker or shuttle tanker removes oil from the storage barge and carries it to an onshore processing facility. It requires perhaps one to three days to transfer the stored oil to the offloading tanker. It may be noted that the production facility may include a platform, spar, TLP (tension lag platform), etc. to enable initial drilling of wells and maintenance and workover of existing wells.
A crew is commonly left on the storage barge at all times. The permanent crew members operate cargo and ballast pumps, provide maintenance and monitor proper operation of equipment on the barge. A seawater ballast system operated by the crew, compensates for changes in weight distribution during loading and unloading to assure barge stability at all times and assure that the strength limits of the vessel are not exceeded. The cost of the permanent crew of perhaps 50 people is substantial and it would be desirable if the barge could operate without them.
In accordance with one embodiment of the present invention, a storage barge is provided for receiving a constant flow of hydrocarbons from an offshore production facility and storing the liquid hydrocarbons, or oil, and for occasionally offloading the oil onto a tanker, where the barge is constructed so it can operate without a permanent crew. Instead, a crew boards the barge only during offloading, which occurs about once a month and lasts perhaps one to three days. The barge has a plurality of rows of tanks, each row extending along the length of the barge, with the tanks in a row being connected in series. Where oil from each row is removed by pumping from one end of the barge such as the bow end, there will be a slow flow of the last amounts of oil to the frontmost or bow tank. To facilitate such flow, the permanent ballast causes the barge to assume an orientation wherein bottom walls of the tanks in a row are angled between 0.5xc2x0 and 8xc2x0 from the horizontal so oil flows downhill towards the frontmost tank when the tanks are almost empty.
The barge is designed to not have a permanent crew onboard, but to have only a small temporary crew during offloading. This is accomplished by eliminating powered systems such as a seawater ballast system and conventional hydrocarbon-fueled power center, and using automatic and remote controlled systems to perform functions with power obtained from solar cells and batteries. The barge has a permanent unpowered ballast system, which eliminates a major prior need for permanent crew members.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.